Recently, the Federal Communication Commission approved usage of the 77 gigahertz (GHz) radio band for the automobile radar market. To operate at this ultra high frequency band, a transistor must have a peak transit frequency, fT, of approximately 200 GHz and a maximum oscillation frequency, fMAX, of >200 GHz.
Currently, the majority of silicon-based products operating in the high frequency bands use SiGe BiCMOS (silicon germanium bipolar complimentary metal oxide semiconductor) technologies. For many of these products, a peak maximum oscillation frequency of 100 GHz is sufficient. In contrast, products operating in the 77 GHz band will most likely require use of a BiCMOS (bipolar complimentary metal oxide semiconductor) technology, including a much higher performance SiGe HBT (silicon germanium heterojunction bipolar transistor) device.
Accordingly, a need exists for a manufacturing process for a HBT (heterojunction bipolar transistor) that can be used at the 77 GHz radio band.
For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements.
The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms “comprise,” “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly coupled in an electrical or non-electrical manner.